Term
Acetylcholine:
Quaternary ammonium (X BBB)
Has muscarinic effects at low doses but w/ atroprine blocking M R's and higher doses it acts like nicotine (NB that stimulation of Nn & Nm is initially stimulatory (of sympathetic ganglion & vasoconstriction -> inc. BP, & secondary rise from catecholamine release) but then is inhibitory) |
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Definition
Axn on CVS: Vasodilation via M3 R's (not innervated); and negative chronotropic (rate), dromotropic (SA & AV conduction), inotropic effect (contraction), via M2 R's coupled to Gi (which also increases K+ permeability and thus hyperpolarizes)
NOTE: IV small dose of Ach -> vasodilation (M3) -> reflex tachy (Beta1). Larger doses -> direct effect brady via M2 R's PLUS vasodilation => this hypotension still superseeds the direct effects -> reflex sympathetic discharge -> tachy |
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Term
Bethanechol:
A choline ester thus not hydrolyzed by AchE, the acetate of Ach is replaced by carbamate & choline is methylated.
Strongly muscarinic w/ no nicotinic axn |
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Definition
BBB - Bethanechol stimulates Bladder and Bowel
It also used alternatively to Pilocarpine for Xerostomia (to promote salivation) as it has less diaphoresis.
It was in the past used for GURD but now is replaced by these two prokinetic agents: Metoclopramide (Cholinergic agonist + dopamine antagonist) OR Cisapride (Cholinergic agonist + serotonin agonist) |
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Term
Carbachol:
Like Bethanechol is a carbamic acid ester.
Works on both M & N R's |
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Definition
| Highly potent and long T1/2 thus not used clinically except as a miotic agent to decrease IOP |
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Term
Methacholine:
Mainly a M R agonist w/ lil N R axn;
Hydrolyzed by AchE but totally resistant to non-specific cholinesterase or butyrylcholinesterase |
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Definition
| Used to Dx bronchial hyperreactivity & asthmatic conditons; is also another alternative to pilocarpine |
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Term
Muscarine:
Natural alkaloid |
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Definition
| Exclusively acts on M R's |
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Term
Arecoline:
Natural alkaloid |
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Definition
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Term
Pilocarpine:
Natural alkaloid, tertiary amine (able to cross BBB to cause CNS disturbances BUT is useful in crossing conjunctival membrane), stable to AchE, M partial agonist |
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Definition
| Has a dominant M axn but has irregular (anomalous) CV axn, but sweat glands are particularly sensitive. Used clinically a sialagogue (saliva) & miotic agent to Tx closed-angle (acute angle-closure) glaucoma (replaced by Timolol - Beta antagonist). NB that other things that help with glaucoma are osmotic agents (oral glycerol & IV mannitol) |
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Term
Nictotine:
Natural alkaloid ??? along w/ lobeline???
Tertiary amine thus crosses placental membrane and secreted in milk along with causing mental confusion in acute nicotine poisoning |
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Definition
In low doses it acts on ganglions to cause activation of both sym and parasym. In the heart its more sym (NB that nicotine has a direct sympathomimetic axn on aortic and carotid bodies which usually cause reflex vasoconstriction and tachycardia).
In the GI, UT, bronchi and salivary glands its parasympathomimetic.
At High doses now it causes ganglionic & neuromuscular blockade cause of prolonged depolarization.
Also note that MCC of Acute Nicotine Poisoning is paralysis of respiratory muscles &/ or central respiratory failure (?bodies?) |
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Term
| Tetramethylammonium & DMPP |
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Definition
| Synthetic compound that differ from nicotine in that they are not followed by a ganglionic blockade. Not used clinically but only as experimental tool |
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Term
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Definition
| Partial agonist @ neuronal nicotinic receptors. Used to aid smoking cessation. Given orally |
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Term
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Definition
| Quaternary ammonium, used to Dx Myasthenia gravis & Eaton-Lambert syndrome, where IV infusion leads to a short increase in strength, also used to reverse neuromuscular block by non-depolarizing muscular blockers |
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Term
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Definition
| Tertiary amine, used in: intestinal & bladder atony, glaucoma (3), OD of anticholinergic Rxs. NB that it shud not have given to TCA OD pts as it could aggrevate depression of heart |
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Term
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Definition
| Quaternary ammonium, more effect then physostigmine on NMJ as it has a direct effect on the N Rs aswell, also stimulates bowel and bladder, antidote for tubocurarine, symptomatic Tx of myasthenia gravis |
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Term
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Definition
| Quaternary ammonium, Tx of myasthenia gravis |
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Term
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Definition
| Covalently binds to AchE, no liposoluble as the others in this grp (thus not able to reach the CNS), is used for chronic glaucoma or management of glaucome if surgery was not done or after other surgeries (non-uveitic type after cataract surgery) |
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Term
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Definition
| Activated in body by conv to O2 analogs, rapidly metabolised but not in insects, the latter is not so readily metabolized by vertebraes |
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Term
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Definition
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Term
| Tacrine, Donepezil, Rivastigmine, Galantamine |
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Definition
| Inhibit AchE, given orally and Tx Alzheimer's |
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Term
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Definition
| Reactivated inhibited AchE before ageing so that it can split the phosphate-enzyme bond in insecticide poisoning, positively charged thus no CNS entry, used empirically even in carbamate intox just to be safe nah |
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